Timing axis for cathode ray oscillographs



Dec. 24, 1935. P. HOOVER ET AL 2 TIMING IS FOR CATHODE RAY OSCILLOGRAPHS v Filed Oct. 19, 1954- I 1 I i I I I I I I =1 5 9% I 10 Z l ATTORNEY Patented Dem 24,1935 t 2 025 20 r UNITE-D STATES PATENT TIMING AXIS FOR CATHODE RAY OSCILLOGRAPHS' Paul L. Hoover, Middlebush, and Evan D. Kennedy, New Brunswick, N. J., assignors to Endowment Foundation, New Brunswick, N. J., a corporation of New Jersey Application October 19, 1934, Serial No. 748,986 10 Claims. (01.171-95) This invention relates to a circuit arrangement 4 by means of a switch H. One of the seconespecially adapted for use in connection with a daries i2 of the transformer 9 supplies currentto cathode ray oscillograph, whereby a. suitable timthe filament or heater of tube l3, while the secing axis is provided. Such a circuit is usually ondary id of the transformer 9 suppliescurrent 5 referred to as a sweep circuit. to the filament of tube I5, the other remaining 5 Our Patent 1,978,461, issued October 30, 1934, winding ll of the transformer 9 being connected sets forth the limitations of prior art circuits of to the filaments of rectifiers 6 and l. this type, and then goes on to describe an ar- Associated with the filter 8, is a voltage divider rangement which will give a timing axis for 9. I8 having a tap l9 extending to the grid-plate- 10 cathode ray oscillograph that will operate at an screens 20 of the tube l3. Another tap 2! extends l0 n ly high speed, that is, on the order of to the balancing resistance 22 (if the tube 15. A one million cycles or more. further tap 24 extends to a rather high resistance In our work with the circuit arrangement set 25, of approximately 50,000 ohms. Interposed forth in our Patent 1,978A61, we have madethe between these various taps and the terminals of further discovery that by properly proportioning the voltage divider I8 are the condensers I6, 23, 15

certain of the circuit elements, we can do away 34 and 35. entirely with the condenser included in the An adjustable resistance 26 is connected across 1 sweep" circuit of our patent, together with the the grid 21 of the tube i3 and one end of the means required to charge this condenser at a voltage divider IS. The resistance 26 is relatively constant rate, as well as the tube for controlling low, being of the order of 1,000 ohms. An adthe charging and discharging of this particular justable resistance 28 of the order of 10,000 ohmscondenser, thereby greatly simplifying and reducis connected to one extremity of the voltage diing the cost of the apparatus required in such' a vider I8 at 36, and to the plate 29 of the. tube l5, circuit, without sacrificing the high speed of opand also to one side of a variable condenser 30,

oration; in fact, our new arrangement to be the other side of which is connected to the grid 25 described herein, is even faster in its operation 21 of the tube I 3. In order to get a considerable than the sweep circuit of our patent referred to. range of capacity. e condenser 30 may e It is therefore the principal object of our inbridged by a fi dj e o e e u vention to provide a relatively simple and inexin the claims .W r f to One (Jr-both 85 a 0011- 30 pensive arrangement or combination of parts denser. The grid 3| of the tube I5 is coupled to 30 which will deliver directly from the oscillator per the plate 33 of the tube l3 and the resistance 25. se, a wave form bearing the characteristics that In the operation of our circuit, when the source will operate a cathode ray oscillograph at a very of alternating current is supplied to the transhigh speed of a million cycles or more per second. former 9, by closing the switch i I, the current is 35 In the drawin a c mp n ing this speciflcasent through the filaments or heaters of the tubes 35 n; I-3 and i5. On closing' the switch 3, power is Figure 1 illustrates a diagrammatic arrangeapplied to the transformer I, the output of which, ment of our improved form of timing axis or at approxi 5 volt pas e t u e "sweep" circuit. a rectifier tubes 8 and l and the filter circuit 8,

40 Figure 2 is a curve showing the charging charimpressing on the voltage divider i8 a smooth 40 acteristics of the main control condenser or condirect current. densers used in our circuit. From the various voltage taps l9, 2!,24 and 38 Figure 3 is a characteristic curve of the current on the voltage divider, current will flow through flowing into said main control condensers. the resistance 25 into the plate 33 of .tube i3.

5 Figure 4 is a curve showing the characteristics Current also starts flowing through resistance 28 of the voltage applied to the circuit extending to into condensers 30 and 32, through the resistance the osciilograph. V 26, back to the potential divider. The condensers In the drawing, 1 is a transformer having its 30 and 32 thus start uncharged, but due to the primary 2 connected by a switch 3 to a source current flowing into them, they become charged of power 4 which may be I I0 volts A. C. The and a voltage is developed across their terminals, 50

secondary 5 of the transformer l' is connected to If the tube It draws no current through its plate 1 rectiflertubes G and 1 which furnish current to circuit, the condensers 30 and 32 will merely be the filter arrangement generally referred to by charged through resistances 28 and 28, and the the numeral 8. The second transformer 9 has rate of charge, as afunctlon of time, will be its primary III a so co nected to the power leads shown as in Figure 2. The maximum value of the voltage on the condensers 30 and 32, will be the voltage on the potential divider, and current into the condensers 30 and 32 and through resistances 26 and 28, will be substantially as shown in Figure 3.

At theinstant of starting, the voltage on the plate 29 of the tube [5 is practically zero, but this starts to build up with time in a manner quite similar to Figure 2. However, due to'the fact that the charging current into condensers '30 and 32 flows through resistance 26, the grid 21 of tube l3 starts in with a positive bias, and this also decreases with time according to Figure 3 in the same manner as the current.

The tube l3 and resistance 25 constitute merely a direct connected amplifier, and thus the output impressed'on the grid 3| of tube 15 is of the same form, except for a reversal of' sign; that is, as the grid voltage of tube l3 decreases with time, the grid voltage of tube l5 increases with time, and vice versa. The net result then is that immediately after the power is applied to the circuit, condensers 30 and 32 are charged through resistances 26 and 28. The tube l5 passes very little current at the start, but rapidly begins to pass more and more, since both plate and grid voltages are becoming more positive. The condition is soon reached where tube l5 passes more current than the resistance 28. This is possible, since'thecurrent into the condensers 33 and 32 reverses and discharges these condensers. This reversal of current into condensers 3i] and .32 also reverses the direction of flow through the resistance 26, which in turn drives the grid of tube I3 negative and consequently the grid of the tube l5 still more positive. As a result, this discharge current will flow until the condensers 30 and 32 are substantially completely discharged. In this discharged state, the voltage across the condensers is practically zero, as is also the voltage on the plate 29 of the tube l5, and conditions are the same as when the voltage was first applied. The cycle is then repeated.

The voltage on the plate 29 of the tube l5 across the terminals 31, which are connected to a cathode ray oscillograph, thus increases from a low value to a relatively high one, several hundred volts, and then rapidly drops to a low value, this cycle repeating as long as power is applied to the circuit. We have found, even with ordinary commercial tubes, that by suitably adjusting the taps on the voltage divider I, it is possible to get a voltage delivered to the terminals 31, that is,

to an oscillograph, which is a linear function of time during the charging interval, and the return time is small compared with the charging time, all as depicted in Figure 4.

The description of the mode of operation of this sweep circuit as given above is from the point of view of oscillator action. It is important to note, however, that in this oscillator a non-linear charging current to the condensers 30 and 32 is combined with another non-linear tube current in order to produce a linear voltage rise with time across the terminals 31. In. other words, two different non-linear currents are used to produce a linear voltage rise across a part of the circuit.

If desired, for the purpose of stabilization, a small coupling condenser 38 may be connected to the circuit under investigation. Such a condenser connected as shown serves to keep the sweep circuit exactly in step with the wave form under examination. Preferably the apparatus is enclosed in suitable separate metal shields as indicated by the dotted lin$ 3. and 40.

We have found that by properly mounting the various tubes and resistances, and by proper adjustment of the other elements--such as the taps on the potential divider and the main control condensers-we can get an oscillator which will 5 deliver directly 2. suitable wave form for a cathode ray oscillograph, which is much faster in its operation than other circuits heretofore used. This is undoubtedlydue at least in part to the simplicity of the arrangement with the minimum 10 number of elements therein, which acts to reduce stray capacities and other disturbances.

What we claimis:

1; Means for supplying electrical energy of suitable wave form for the deflection plates of a cathode ray oscillograph; said means including a pair of electron tubes having a resistance coupling including a source of voltage between the plate of one tube and the grid of the other, a second coupling between the grid of the one tube and the plate of the other tube; said second coupling including, an adjustable resistance in each of the said grid and plate circuits and a source of voltage; and an adjustable condenser connected between said last-mentioned grid and plate, the plate output terminals of said other tube adapted to be directly connected to the oscillograph.

2. Means for supplying electrical energy of suitable wave form for the deflection plates of a cathode ray oscillograph; said means comprising an oscillator circuit including a pair of electron tubes having the plate of one coupled to the grid of the other, also the grid of the one coupled through a condenser to the plate of the other, the first coupling being supplied with an adjustable voltage through a high'resistance, while the other coupling is supplied on opposite sides of said condenser with voltages through adjustable resistances, the plate output terminals of said other tube adapted tobe directly connected to 40 the oscillograph,

3. Means for supplying electrical energy of suitable wave form forthe deflection plates of a cathode ray oscillograph; said means comprising,

a source of selectable voltages, a pair of electron tubes having the plate circuit of one of the tubes adapted to be connected to the oscillograph, while the output side of the second tube is coupled through a resistance type coupling to the input side of the first tube with means for-supplying a variable voltage thereto from said source of voltages, while the input side of the second tube is connected to the output side of the first tube through an adjustable condenser, voltages being applied from said source to said last-mentioned input and output sides of the tubes through suitable adjustable resistances.

4. Means for supplying electrical energy of suitable wave form for the deflection plates of a cathode ray oscillograph; said means comprising an oscillator circuit including a pair of electron tubes-resistance-coupled together with a source of adjustable voltage connected to the resistance, said source of voltage being connected to the input and output circuits of the tubes through ad- 5 justable resistances with an adjustable condenser bridging said input and output circuits, the output terminals of the oscillator circuit adapted to be connected to the oscillograph.

5. Means for supplying electrical energy of suitable wave form for the deflection plates of a cathode ray oscillograph; said means comprising an oscillator including two electron tubes coupled in part by a resistance coupling so that one of the tubes acts as an amplifier to the other, said tubes being further coupled through an adjustable condenser with a source of voltage applied through adjustable resistances to opposite sides of the condenser, the plate output terminals of said second tube adapted to be connected to the oscillograph.

6. A "sweep circuit arrangement as set forth in claim 5, further characterized in that said amplifier tube includes a grid-plate screen and a.

voltage divider having taps thereto which supplies energy to the whole circuit arrangement. said grid-plate screen being connected to a tap on said voltagedivider.

7. Means for supplying ultra-high frequency energy to a cathode ray oscillograph; including a condenser, a pair of electron tubes coupled by the condenser, the grid of one tube to the plate of the other tube, a source ot'unidirectional voltage, adjustable resistances connected between said source or voltage and said grid and plate, and a further coupling between the plate and grid of said respective tubes, said coupling including a resistance connected also to a variable tap on said source of voltage, the plate output terminal of one of the tubes adapted to be connected to the oscillator.

8. Means for supplying electrical energy of suitable wa've form for the deflection plates of a cathode ray oscillograph; said means comprising an oscillator including two electron tubes coupled in part by a resistance coupling so that one o! the tubes acts as an amplifier to the other, said tubes being further coupled through a condenser, the

opposite terminalsof which are connected through suitable resistors to a source of uni-directional current, whereby thecondenser charge has a nonlinear characteristic and the non-amplifier tube of the oscillator also has a non-linear-characteristic, the combination or the two non-linear characteristics producing substantially a straight line voltage-characteristic which is supplied to the circuit leading to the oscillograph.

9. Means for supplying ultra-high frequency electrical energy to the deflection plates of a cathode ray oscillograph directly from the plate circuit of an electront'ube; said means including, a second electron tube coupled as an amplifler to the grid of the first mentioned tube, acondenser coupling the grid of the amplifier tube to the plate or the first-mentioned tube and a source 01' uni-directional current connected through suitable impedances to the opposite sides of the condenser as well as to the' amplifier coupling between said tubes. a 1 10. Means for supplying electrical energy of suitable wave form for the deflection plates of a cathode ray oscillograph; said means including a *e ircuit wherein a plurality of non-linear voltages 

